Internal combustion engines often incorporate exhaust gas recirculation (EGR) systems to improve exhaust gas quality and fuel efficiency of the engine. In an internal combustion engine, where peak combustion temperature can exceed 2,500 degrees F. (1,372 degrees C.), nitrogen in the air reacts with oxygen to produce nitrous oxides (NOx). To reduce the level of NOx emissions, an EGR system routes a portion of the exhaust gas to a location upstream of the internal combustion engine where it is mixed with the fresh air supply and then recirculated to the internal combustion engine. The mixture of the exhaust gas with the fresh air supply dilutes the incoming fuel charge, thereby lowering flame temperatures. One location for mixing the exhaust gas with the fresh air supply may be at the intake manifold of the engine.
For internal combustion engines incorporating an EGR system, tubes through which the exhaust gas is routed to the intake manifold run external to the intake manifold, and therefore, more space is required in an engine compartment in which the internal combustion engine and intake manifold are housed. However, weight and space restraints are becoming more critical in vehicles as the designs are becoming more streamlined. One area in which a reduction in space is desired is the engine compartment.
Therefore, there exists a need for an intake manifold incorporating exhaust gas recirculation in a more compact manner to reduce the amount of space that the intake manifold may occupy, for example, within an engine compartment of a vehicle.